When you have completed editing your m4 configuration file, you must process it to produce the /etc/mail/sendmail.cf file read by sendmail. This is straightforward, as illustrated by the following example:
# cd /etc/mail # m4 /usr/share/sendmail.cf/m4/cf.m4 vstout.uucpsmtp.mc >sendmail.cf
This command invokes the m4 macro processor, supplying it the name of two macro definition files to process. m4 processes the files in the order given. The first file is a standard sendmail macro template supplied with the sendmail source package, the second, of course, is the file containing our own macro definitions. The output of the command is directed to the /etc/mail/sendmail.cf file, which is our target file.
You may now start sendmail with the new configuration.